OLYMPIA — The Washington State Department of Agriculture is working to expand its apple maggot quarantine rule to include the potted soil of host plants.

The department posted a notice Nov. 14 that it started a rule amendment process. No draft is ready yet nor public comment period set. Jim Marra, pest program manager of the department’s plant protection division, said he doesn’t anticipate any amendment going into effect until late 2018 or early 2019. A Small Business Economic Impact Statement has to be completed first and that can take time, he said.

Apple maggot, also known as a railroad worm, is a pest of several fruits, mainly apples. It has long been active on the East Coast but was discovered in Portland in 1979. It’s been active in western Oregon and Washington and slowly spread east of the Cascades as a low-level problem in backyard fruit trees and has never been detected in commercially packed fruit.

The department and Washington State Tree Fruit Association want to keep it that way.

“Our big concern is big box stores. If plants are coming in there that have produced fruit or are fruiting,” said Ranie Haas, director of regulatory and industry affairs for the association in Yakima.

In a July 17 letter to Marra, Haas said failure to control apple maggot would require growers to increase costly pesticide applications to prevent crop loss. Lack of adequate control also jeopardizes access to foreign markets for the fruit, she said. Potted nursery trees and their soil are potential pathways for spread of apple maggot, she said.

The current rule requires inspection and certification of apples, crab apples, hawthorn, apricots, cherries, plums, prunes and quince, but not commercial pears, as pest-free before being sold if an apple maggot fly is found within half a mile of an orchard. If fruit is infested it must undergo cold storage and treatment before exporting.

Homegrown or foraged fruit cannot be moved from a quarantine area into or through a pest-free area. Quarantined areas include all of Western Washington, the western half of Chelan County, Kittitas County, the western and northern two-thirds of Yakima County, Klickitat County, the southeastern portion of Lincoln County and Spokane County.

In 2016, the rule was amended to require composting companies to treat municipal yard wast to kill apple maggots before trucking material into apple-growing regions for processing.

Specific language is under discussion for the new potted soil amendment, Marra said.

The idea is to prevent nurseries from shipping infected host plants — which are the same as those on the certification list — and their potted soil into tree fruit regions of Eastern Washington. Non-commercial cherries and pears would be on the list and commercial cherries and pears would be exempt, he said. Only host plants old enough to have fruited would be regulated, he said. Non-bearing plants and rootstock would not be regulated.

“If nurseries are shipping from an apple maggot pest-free area to a pest-free area they will not be regulated,” Marra said. As with orchards, nurseries will have the option of trapping all hosts within half a mile of the nursery, he said. If no apple maggots are caught, they will be free to ship.

“We are looking into the possibility of allowing host plants that have had soil treatments of some kind but none have been identified so far,” he said.